THE PROBLEM OF U.K.R. REVISIONS

Abstract

In last ten years U.K.R. number increased due to diffusion of M.I.S. concepts, new indications/tecniques and durable prosthetic models. Also the amount of revisions, performed for different reasons, has increased. Failures relate to planning and surgical errors, aseptic loosening, non treated or femoro patellar compartment degeneration, ligaments instability, P.E. wear, components ruptures, infections.

In our division in 1990–2003 we performed 136 U.K.R. revisions on 13 different implants with a prevalence of “fixed bearing” (79,40%) on “meniscal bearing” (20,60%). A classification withprevalence of failure causes, different from T.K.R.’s, is proposed. Revision procedure strongly depends on causes: “Uni”, “BiUni” or “Total” approach is possible. We present our experience and derived indications.

Aseptic loosening were treated differently depending on bone stock and on failure risk factors (ligament laxity, surgical osteotomic or axial errors, fixation defects) with a “Uni” revision or with a “Total”. Unicompartimental degeneration with a previous medial or lateral U.K.R. in good conditions may undergoes “BiUni” instead of “Total” only in absence of ligament laxity and femo-ropatellar symptomatic degeneration. Femoro-patellar degeneration needs a T.K.R. implant. We managed cases with macroscopic surgical errors (ostheotomy or component alignment) by using T.K.R. (stemmed and with auto-graft if needed) and U.K.R. revision. Failures due to varus-valgus instability were normally treated with T.K.R. (standard or stemmed) and with constrained T.K.R. (1 Reumatoid Arthritis case). We resolve P.E. debris failures in fixed bearing implants simply with a component change as we do in stress fractures (femur or “full poly” tibia). We treat infections with a 2 step procedure; for 2°step we used T.K.R. (standard or stemmed).

In conclusion U.K.R. revision is technically easier than TKR’s, bone stock defect may be fighted with auto graft and/or stems and in a selected amount of cases it’s possible to use U.K.R. orstandard T.K.R. with very similar long term results of first implants.